b3£.£3L 

( 

635.21 

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A 

— X 


STATES  DEPARTMENT  OF  AGRICULTURE 


, 


BUREAU  OF  PLANT  INDUSTRY 

OFFICE  OF  COTTON,  TRUCK,  AND  FORAGE  CROP  DISEASE  INVESTIGATIONS 

and 

OFFICE  OF  HORTICULTURAL  AND  POMOLOGICAL  INVESTIGATIONS 
•  WASHINGTON,  D.  C. 


GROWING  HIGH-GRADE 

SEED  STOCK 


POTA^QbRARY  r'- 
AUG  13  1 

UNIVERSITY  0£  U 


r 


Type  Specimens  of  Triumph  Potatoes 


1 


C.,  T.,  &  F.  C.  D.  Circular  5 


Issued  July  15,  1918 


e 


Fig.  1.— A  potato  plant  showing  mottling  and  crinkling  of  the  leaves,  a  type  which  is  undesirable  in  the 

seed  plat. 


GROWING  HIGH-GRADE  POTATO  SEED  STOCK. 


FARMERS  may  obtain  better  seed  potatoes  for  next  year  by 
giving  the  subject  a  little  special  attention  this  summer. 
Next  fall  will  be  too  late.  The  old  methods  of  selecting  the 
most  perfect  tubers  from  the  bin,  rejecting  those  showing  de¬ 
fects,  and  treating  with  chemicals  for  disease  control  are  good  as 
far  as  they  go;  but  they  fail  to  reach  the  destructive  seed-borne  dis- 
^  eases  ancL weaknesses  which  do  not  change  the  appearance  of  the 
seed,  and  they  do  not  necessarily  eliminate  varietal  mixtures. 

WATCH  THE  PLANTS. 

A  much  greater  measure  of  success  may  be  obtained  if  careful 
selection  is  carried  out  on  the  plants  during  the  summer.  Varietal 
mixtures  and  weak  and  diseased  plants  can  readily  be  detected  and 
removed  from  the  growing  crop. 

HAVE  A  SEED  PLAT. 

In  seed-producing  sections  all  progressive  growers  should  maintain 
a  seed  plat  for  the  purpose  of  improving  their  own  seed  supply. 
The  seed  plat  may  be  either  a  separate  field  or  a  portion  of  the  com¬ 
mercial  planting  set  aside  for  special  attention.  An  area  of  one-tenth 
to  one-fifteenth  of  the  entire  acreage  will  usually  provide  sufficient 
seed  for  the  following  season’s  planting. 

BEGIN  THIS  SUMMER. 

While  it  is  an  advantage  to  start  the  seed  plat  with  selected  mate¬ 
rial,  the  work  may  be  begun  during  the  growing  season  with  any 
good  stock  of  promising  quality  planted  in  suitable  soil  and  properly 
cared  for.  The  essential  requirements  are  (1)  stock  of  good  potential 
vigor  reasonably  free  from  disease,  (2)  suitable  soil,  (3)  adequate  but 
not  excessive  fertilization,  (4)  good  cultivation  and  care,  (5)  careful 
elimination  of  undesirable  hills  during  the  progress  of  the  season, 
(6)  proper  whiter  storage,  (7)  thorough  sorting,  and  (8)  treatment 
with  chemicals  (if  necessary)  before  planting  the  next  season.1 

1  For  a  more  detailed  discussion  of  the  methods  and  limitations  of  seed  treatment,  see  “Selection  and 
treatment  of  seed  potatoes  to  avoid  diseases,”  Bureau  of  Plant  Industry,  C.,  T.,  &  F.  C.  D.  Cir.  3,  which 
may  be  obtained  free  of  charge  from  the  Division  of  Publications,  United  States  Department  of  Agricul¬ 
ture. 

66953°— 18  3 


/ 


4  GEOWING  HIGH-GEADE  POTATO  SEED  STOCK. 

START  WITH  A  GOOD  STRAIN. 

Stock  of  any  adapted  standard  commercial  variety  of  good  poten¬ 
tial  vigor  is  suitable  provided  it  is  reasonably  free  from  disease,  par¬ 
ticularly  from  the  tuber-borne  troubles  of  the  degenerate  type  men¬ 
tioned  later.  Stock  that  produces  more  than  a  small  percentage  of 


Fig.  2.— A  type  of  plant  undesirable  in  thd seed  plat. 

weak  or  degenerate  hills  does  not  respond  well  to  selection,  but  is 
almost  sure  to  give  disappointing  results.  It  is  better  to  discard 
doubtful  strains  entirely,  disposing  of  them  for  table  use  and  replac¬ 
ing  them  with  stock  from  new  sources  of  known  satisfactory  per¬ 
formance  and  yield. 

GROW  THE  PLANTS  WELL. 

A  superior  grade  of  seed  potatoes  can  not  be  produced  unless  the 
plants  are  provided  with  good  growing  conditions.  The  best  portion 
of  the  field,  therefore,  should  be  selected  for  the  seed  plat.  Good 
drainage  is  essential.  A  sandy  or  gravelly  loam,  with  clover  or  alfalfa 
sod,  is  preferable  to  other  soils,  though  not  absolutely  necessary. 


GROWING  HIGH-GRADE  POTATO  SEED  STOCK. 


5 


Deep  cultivation  during  the  early  growth  of  the  plant,  followed  by 
shallower  ones,  assists  in  developing  a  good  vigorous  root  growth 
and  also  serves  to  conserve  the  moisture,  as  well  as  make  larger 
amounts  of  plant  food  available.  The  number  and  frequency  of  the 
cultivations  should  be  governed  by  the  character  of  the  season  and 
the  soil.  Neglect  in  cultivation  is  not  conducive  to  the  production 
of  a  superior  grade  of  seed  stock. 

SPRAY  EARLY  AND  WELL. 

In  regions  subject  to  early-blight  or  late-blight,  thorough  spraying 
with  Bordeaux  mixture  under  high  pressure  should  be  practiced0 
Spraying  also  aids  in  the  control  of  the  flea  beetle  and  of  tip-burn. 


Fig.  3. — Another  type  of  plant  undesirable  in  the  seed  plat. 

It  is  highly  essential  to  make  the  first  application  for  the  control  of 
late-blight  early,  before  the  lower  leaves  are  sheltered,  so  that  they 
may  be  thoroughly  covered;  otherwise  they  become  serious  centers 
of  infection  during  the  critical  period  later.  After  this  first  applica¬ 
tion  it  is  necessary  to  spray  only  to  cover  the  new  growth  as  it 
develops. 

ELIMINATE  ALL  VARIETAL  MIXTURES  AND  DISEASED  AND  WEAK  HILLS. 

Several  times  during  the  season  the  seed  plat  should  be  inspected 
by  walking  the  length  of  each  row,  observing  the  individual  plants 
for  evidence  of  disease.  The  weak,  degenerate,  and  diseased  hills, 


6 


GROWING  HIGH-GRADE  POTATO  SEED  STOCK. 


and  varietal  mixtures  should  be  pulled;  and,  if  tubers  have  formed, 
these  should  be  dug  out  and  removed  from  the  field  at  the  time, 
so  that  only  the  progeny  of  healthy  hills  of  the  correct  variety 
will  remain  at  harvest  time.  It  is  necessary  to  go  over  the  plat 
at  least  two  or  three  times  in  order  to  detect  all  the  objectionable 
plants.  Varietal  mixtures  are  most  readily  found  when  the  plants 
are  in  bloom.  Some  diseases  are  seen  early,  whde  some  develop 
only  later.  The  plants  to  be  removed  may  be  considered,  for  prac¬ 
tical  purposes,  as  belonging  in  the  following  groups:  (1)  Varietal 
mixtures;  (2)  plants  showing  stem-rot  either  at  or  below  the  surface 


Fig.  4.— A  potato  plant  showing  a  peculiar  rolling  of  the  lower  leaves,  a  type  which  is  undesirable  in  the 

seed  plat. 

of  the  soil  (black-leg  and  Fusarium  stem-blight);  (3)  plants  develop¬ 
ing  any  type  of  abnormal  rolling  of  the  leaves,  whether  leading  to 
premature  death  of  the  plant  or  not  (Fusarium  wilt,  Verticillium  wilt, 
Fusarium  blight,  Rhizoctonia  rosette,  late  black-leg,  leaf -roll,  curly- 
dwarf);  (4)  plants  with  mottled  or  mottled  and  crinkled  leaves 
(mosaic,  mosaic-dwarf,  and  curly-dwarf),  (5)  evidently  stunted, 
weakened,  or  unthrifty  plants.  (Figs.  1-4.)  All  the  diseases  enu¬ 
merated  above  are  carried  from  season  to  season  by  seed  tubers. 
Only  the  Rhizoctonia  and  Fusarium  troubles  are  known  also  to  be 
carried  over  in  the  soil,  unless  it  may  be  the  rather  uncommon  but 
destructive  leaf-roll,  about  which  evidence  is  incomplete  and  opin¬ 
ions  differ. 


GROWING  HIGH-GRADE  POTATO  SEED  STOCK. 


7 


Mosaic  deserves  special  attention.  This  trouble  is  becoming 
widespread  and  serious  on  certain  varieties  like  the  Green  Mountain 
and  Bliss  Triumph.  In  badly  infected  stock  a  large  proportion  of 
the  diseased  plants  become  dwarfed,  have  crinkled  foliage,  and  fall 
very  low  in  productivity.  The  Bliss  Triumph  variety,  grown  ex¬ 
tensively  for  the  southern  seed  trade,  is  so  generally  infected  that 
many  experienced  growers  erroneously  consider  the  crinkled,  mot¬ 
tled  leaf  normal  for  the  variety.  The  cause  of  the  mosaic  is  unknown, 
and  no  complete  means  of  control  has  been  found,  but  rigid  roguing 
in  the  seed  plat  eliminates  the  dwarfed,  stunted,  low-yielding  plants 
from  the  progeny  the  following  year,  greatly  increasing  the  yield.  It 
is  profitable  to  remove  all  mosaic  plants  from  the  seed  plat,  even  if 
it  amounts  to  hah  or  two-thirds  of  the  total  number,  as  it  may  the 
first  year.  This  wi’l  not  entirely  eliminate  the  disease,  and  it  is 
probable  that  a  proportion  of  the  progeny  will  still  show  some  signs 
of  mottle-leaf,  but  the  dwarfed  plants  will  be  absent  or  few.  The 
.second  year  the  seed  plat  will  contain  a  much  higher  percentage  of 
healthy  plants.  The  mosaic  is  worse  in  the  South  than  in  the  North, 
and  growers  who  produce  Bliss  Triumph  potatoes  for  the  southern 
seed  market  should  certainly  maintain  a  seed  plat  for  their  own 
acreage.  Their  own  yields  will  not  only  be  greatly  increased  theretf^ 
but  the  effect  will  be  reflected  even  more  strikingly  in  the  southern 
fields. 

HARVESTING  THE  SEED  PLAT. 

At  the  close  of  the  season  the  plants  which  have  remained  healthy 
may  be  dug  with  a  potato  digger  and  the  total  yield  saved  for  seed, 
but,  if  time  permits  hand  digging,  a  further  selection  may  advan¬ 
tageously  be  made  by  eliminating  all  the  low-yielding  hills;  also 
those  producing  an  undue  proportion  of  small  or  unshapely  tubers. 
A  further  step  may  be  taken  at  this  time,  which  will  materially  assist 
in  the  subsequent  development  of  a  high-grade  strain  of  seed  potatoes, 
by  selecting  the  progeny  of  the  good-yielding  and  most  uniform 
hills  to  be  used  for  the  planting  of  the  following  season’s  seed  plat. 
See  the  illustration  on  the  title-page.  The  remainder  of  the  seed 
produced  on  the  seed  plat  can  then  be  gathered  for  the  main-crop 
planting  next  year. 

HANDLE  AND  STORE  PROPERLY. 

The  seed  should  be  so  handled  from  the  start  as  to  avoid  unneces¬ 
sary  cutting,  bruising,  or  other  injury,  since  the  vitality  of  damaged 
tubers  is  reduced.  This  can  best  be  accomplished  by  gathering  and 
storing  the  seed  potatoes  in  slat  crates,  thereby  avoiding  any  further 
injury  in  handling.  It  is  desirable  to  place  the  crates  in  storage  as 
soon  as  possible  after  harvesting.  Stored  in  a  cool  and  reasonably 


8 


GROWING  HIGH-GRADE  POTATO 


UNIVERSITY  OF  ILLINOI9-URBANA 


01 


12 


731 


3938 


moist  storage  house,  provided  with  good  ventilation,  and  maintained 
at  a  temperature  of  36  to  40°  F.,  or  as  near  these  figures  as  possible, 
the  seed  should  come  out  in  the  spring  in  almost  as  good  condition  as 
when  placed  in  storage. 


SORT  AND  TREAT  WITH  CARE. 


Before  the  next  planting  time  the  stock  should  be  carefully  worked 
over,  to  remove  all  badly  cut  or  bruised  tubers  and  those  showing 
serious  scab  or  black-scurf  and  decay  of  any  kind.  Tubers  badly  off 
type  should  also  be  discarded,  as  should  any  showing  abnormal 
discoloration  of  flesh,  which  can  be  seen,  of  course,  only  at  the  time 
of  cutting.  If  scab  or  black-scurf  is  present  in  any  degree,  it  is 
advisable  to  treat  the  seed  by  covering  for  30  minutes  in  a  solution 
containing  4  ounces  of  corrosive  sublimate  to  30  gallons  of  water. 

■  -r  * 

BECOME  A  SEED  GROWER. 

The  seed-plat  method  with  potatoes  in  the  hands  of  careful 
growers  promises  to  improve  greatly  the  general  average  of  seed 
stock,  and  it  looks  forward  a  step  toward  the  development  in  America 
■of  a  much-needed  group  of  successful  specialized  professional  potato- 
leecl  growers,  whose  function  will  be  the  production  of  seed  potatoes 
in  distinction  from  potatoes  to  be  sold  for  seed. 

H.  A.  Edson. 

William  Stuart 

Approved:  „T  ubrM«  w£ 

Wm.  A.  Taylor,  Vi.c  13  1940 

Chief  of  Bureau .  Fh  v 

UNIVERSE  0HLUt...> 

o 


June  20,  1918. 


